Adjustable actuating level current sensing relay

ABSTRACT

An adjustable actuating level current sensing relay including a housing mounting a switch having its movable contact coupled with a solenoid coil. A current sensing transformer is mounted on the housing and includes first and second coils having first and second cores. The first and second cores are connected together by means of ferromagnetic adjustment means formed with an air gap which is adjustable to selected spacings by means of an adjustment screw and the second core is connected with the solenoid coil. Consequently, the contacts may be connected in circuit with an electrical operator to be operated, and the first coil of the sensing transformer connected with an electrical element, the electrical condition of which is to control the operator. The adjustment screw may then be adjusted to vary the spacing of the air gap to vary the electromagnetic coupling between the first and second transformer coils to provide for closure of the switch at the desired level of current in the second transformer coil.

Limited States Patent n91 M clntosh et a1.

[ 11] 3,760,309 1 Sept. 18, 1973 ADJUSTABLE ACTUATTNG LEVEL CURRENT SENSING RELAY [75] Inventors: Harold A. McIntosh, South Pasadena; George A. Yeaman, Fallbrook, both of Calif.

[73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: June 22, 1972 [21] Appl. No.: 265,332

[52] 11.8. C1. 335/1, 335/237 [51] lint. Cl. H0lh 47/00 [58] Field of Search 335/1, 266, 237; 336/173, 182

[56] References Cited UNITED STATES PATENTS 1,548,596 8/1925 Ghegan .Q 335/237 1,167,067 1/1916 Hill 335/266 2,527,220 10/1950 Hughes 335/266 2,820,927 1/1958 Steiner 335/266 2,873,412 2/1959 Pratt 335/266 Primary Examiner-Harold Broome Attorney-Vern Schooley et a1.

[57] ABSTRACT An adjustable actuating level current sensing relay including a housing mounting a switch having its movable contact coupled with a solenoid coil. A current sensing transformer is mounted on the housing and includes first and second coils having first and second cores. The first and second cores are connected together by means of ferromagnetic adjustment means formed with an air gap which is adjustable to selected spacings by means of an adjustment screw and the second core is connected with the solenoid coil. Consequently, the contacts may be connected in circuit with an electrical operator to be operated, and the first coil of the sensing transformer connected with an electrical element,the electrical condition of which is to control the operator. The adjustment screw may then be adjusted to vary the spacing of the air gap to vary the electromagnetic cou pling between the first and second transformer coils to provide for closure of the switch at the desired level of current in the second transformer coil.

9 Claims, 4 Drawing Figures 6/ I f 1711 lllh' min BACKGROUND OF THE INVENTION 1. Field of the Invention The adjustable actuating level current sensing relay of the present invention relates to a relay that may be adjusted to actuate at different levels of current sensed thereby.

2. Description of the Prior Art Current sensingrelays have been proposed which operate relay contacts in response to sensing of a predetermined level of current. A current sensing relay of this type is shown in U. S. Pat. No. 3,636,414. However, such current sensing relays suffer the shortcoming that the level of current sensed required to operate such relays cannot be rapidly and conveniently adjusted.

Electromagnetic switches have been proposed which are disposed in the electromagnetic field of an electro- SUMMARY OF THE INVENTION The adjustable actuating level current sensing relay of the present invention is characterized by a current sensing transformer which includes a first and second coil, the second of which is'connected with a driver that controls a switch means and the firstof whichis con-' nected with an electrical element, the current level of which is to actuate the relay. The first and second coils include first and second cores which are magnetically coupled together by means of adjustment means'ineluding ferromagnetic elements normally spaced apart to form a high reluctance gap, the spacing of which may be adjusted to selectively vary the strength ,of the electromagnetic coupling between thefirst and second coils to thereby vary the level of current required in the first coil to actuate the driver for closing the-switch means. Preferably, thefirst coil is easily removable and may conveniently be replaced by a different sized coil to provide a greater electromagnetic force for the same current level therein, thereby rendering such relay readily adaptable for operation in response to a wide range of various current levels sensed by such second coil.

The objects and advantages of th'epresent invention will become apparentfrom a consideration of the following detailed description when taken in conjunction with the accompanying drawing.

DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an adjustable actual;-

2 picting such relay adjusted for actuation in response to different levels of current sensed thereby.

DESCRIPTION OF THE PREFERRED EMBODIMENT The adjustable actuating level current sensing relay of the present invention includes, generally, a housing 11 having a switch 13 mounted thereon and driven by a vertically extending solenoid coil 15 which is connected with a secondary coil 17 of a currentsensing transformer 19. The primary coil 21 of the transformer 19 has a tubular electromagnetic coil 22 carried from the core 24 of the secondary coil 17 by means of slightly resilient electromagnetic flanges or posts 23 and 25. Referring to FIG. 4, the tubular core 22 of the secondary coil 21 is carried from the upper extremities of the resilient flanges 23 and 25 by means of a non-ferromagnetic brass adjustment screw 27 which may be adjusted to vary the spacings between the ends of such core 22 and such flanges to thereby vary the reluctance thereacross and, consequently, the current in the secondary coil. 17 to thereby adjust the current in the solenoid coil 15 to thereby adjust the level of current required in the windings of the primary coil 21 for closure of the switch 13. Y A I The basic construction of the relay housing 11 and switch 13 is the same as that disclosed in U. S. Pat. No. 3,636,414, the switch including first and second spaced apart stationary contacts 31 and 33 carried from respective electrically conductive strips 35 and 37 which project through thebottom wall of the housing to form respective plug prongs 39 and 41. A movablecontact 43 is interposed in the space between the stationary contacts 31 and 33'and is carried from the free ,end of acantileverallymounted electrically conductive leaf spring 45 which is connected on its fixed end with an electrically conductive strip projecting through the bottom wall of the housing 11 to form a plug prong 47.

A pair of solenoid coil plug= prongs 51 are connected across the solenoid coil 15 and in series with the anodecathode circuit of an SCR 53 as disclosed'in the afore mentioned U. S. Pat. No. 3,636,414. The gatecathode circuit of the SCR 53 is connected across the secondary coil 17 to receive a gating current therefrom for triggering to energize the solenoid coil 15.

Overlying thetop end of the vertically extending solenoid coil 15 is a ferromagnetic actuating arm 61 which is carried cantileverally on its rear extremity from a vertical post 63 and is engaged on its free extremity with the free extremity of the leaf spring 45 carrying the movable contact 43 by means of a vertical spacer 65. The opposite extremities of the secondary coilcore 24 are supported from the opposite sides of the housing 11 and the bottom ends of the flanges 23 and 25 are fixed thereto, such flanges raising upwardly through the top wall of the housing 11 and being formed in their upper extremities with respective bores .screw 27, and the opposite end of such 67 and 69, thebore 69 being internally threaded. The bore 67loosely receives the head end of the adjustment screw is threaded and screwed into the bore 69.

The opposite ends of the tubular core 22 of the ,primary coil 21 are formed with axially opening annular wells 71 and 73 which leave annular tips 75 and 77 pro jecting axially therearound for selective contact with the respective flanges 23 and 25 as described hereinafter. Received within the respective wells 71 and 73 are v such an application, the plug prongs leading from the stationary contact 33 and movable contact 43 would be connected in series with the motor to enable such motor to be energized as long as such contacts are closed. The plug prongs 51 connected with the opposite ends of the solenoid coil 15 are then connected with a power source. The approximate current level to which the motor is to be limited is then determined and a bobbin 81 having approximately the number of turns thereon to gate the SCR 53 when the current level in the lead 83 approximates such current level is then selected and placed on the tubular core 22 by disconnecting the adjustment screw 27 and mounting such bobbin on the tubular core 22.

Further adjustment may be made by connecting the opposite ends of the windings 83 from the bobbin 81 with a current source and adjusting such source to the current level at which it is desirable to have the motor drop out of circuit. The adjustment screw 27 can then be rotated to adjust the gaps formed between the opposite ends of the core 22 and the flanges 23 and 25 to adjust the reluctance exhibited by such gaps to a level that will raise the current induced in the secondary coil 17 to a level sufficient to provide a gating current on the gate of the SCR 53 thereby triggering such SCR and completing a circuit through the solenoid coil 15 toenergize such coil and draw the free end of the ferromagnetic actuating arm 61 downwardly thereby drawing themovable contact 43 downwardly to disengage the stationary contact'33. Disengagement of the contacts 33and 43 will open the circuit to the motor thereby preventing further overload thereof.

Once the current through the primary coil 21 has been diminished below the triggering level of the relay, the current from-the secondary coil 17 will drop below the triggering level of the SCR 53 thus rendering such SCR non conductive and opening the current through the solenoid coil 15 thereby de-energizing such coil and freeing the free extremity of the actuating arm 61 to be raised to its elevated position thereby bringing the movable contact 43 back into contact with the stationary contact 33 thus completing a circuit to the motor.

in other applications, the adjustment screw 27 may be further adjusted to vary the gaps between the opposite ends'of the' primary coil 22 and flanges 23 and 25 to further vary the reluctance exhibitedthereby to provide different relay actuating levels for such other applications. Extreme sensitivity may be provided by drawing the adjustment screw 27 entirely downwardly to bring the primary coil tip 75 and 77 into metal-tometal contact with the respective flanges 23 and 25 thereby minimizingthe reluctance between such core and flanges. i i v For other applications, the bobbin 81 may be replaced by a different bobbin having a different number of turns thereonthus further altering the actuation level thereof.

From the foregoing it will be apparent that the adjustable actuating level current sensing relay of the present invention provides a highly flexible relay which will operate in response to a wide range of current levels thereby providing an economic relay for numerous different applications.

What is claimed is:

1. Adjustable actuating level current sensing relay comprising:

a housing;

switch means carried by said housing;

drive means mounted in said housing for actuating said switch means and operative in response to a predetermined voltage to complete a circuit through said switch means; sensing transformer means mounted in said housing and including first and second coil means, said second coil means being connected with said drive means, said transformer means further including first and second spaced apart core means electrically coupledwith said first and second coil means and adjustment means coupling said first and second coil means together for adjusting the space therebetween; sensing means connected with said first coil means for sensing the current level in an electrical element whereby said sensing means may be connected with said element, said switch connected with an electrical operator which is to be operated when the current sensed by said sensing means reaches a predetermined level, said adjustment means adjusted to set said first and second. core means at a spacing which will provide sufficient electromagnetic coupling therebetween when the current in said current sensing means reaches said predetermined level to produce said predetermined voltage and complete said circuit through said switch means.

2. Adjustable actuating level current sensing relay as set forth in claim 1 wherein:

said second core means includes an axial ferromagnetic core projecting through said first coil means and said second coil means includes a pair of spaced apart ferromagnetic support flanges projecting on opposite ends of said core and wherein said coupling means includes non-ferromagnetic screw means connecting said first and second core means together.

3. Adjustable actuatiing level current sensing relay as set forth in claim 1 wherein:

said adjustment means includes resilient electrically insulative biasing means interposed between said first and second core means and biasing said first and second core means apart.

4. Adjustable actuating level current sensing relay as set forth in claim 1 wherein:

said first core means includes an axial core and said first coil means includes a bobbin removably received on said axial core and including a selected number of electrical coil turns thereon whereby said bobbin may be selectively changed.

5. Adjustable actuating level current sensing relay as set forth in claim 1 wherein:

said first core means includes an axial core and said second core means includes a pair of ferromagnetic flanges projecting transversely therefrom and formed in their extremities with respective first and second bores, said second bore being threaded and wherein, further, said first core means includes an said adjustment means includes first and second resilaxial ferromagnetic rod and said adjustment means 5 includes nonferromagnetic screw means projecting through said first bore and through said rod, threaded on one extremity, and screwed into said second bore whereby the spacing between said first and second core means may be adjusted by turning 10 said screw means.

6. Adjustable actuating level current sensing relay as set forth in claim 2 wherein:

said adjustment means includes resilient nonferromagnetic biasing means interposed between one s end of said axial core and the adjacent flange to maintain said adjacent flange and axial core biased 8. Adjustable actuating level current sensing relay as set forth in claim 3 wherein:

at least one of said core means includes a cut back notch for receipt of said biasing means and a projecting contact tab for contacting the other of said core means when said adjustment means is adjusted to draw said first and second core means fully together. 9. Adjustable actuating level current sensing relay as set forth in claim 5 wherein:

said adjustment means includes first and second non-ferromagnetic biasing means interposed between the opposite ends of said first core means apart. and said respective flanges for biasing said respec- 7. Adjustable actuating level current sensing relay as tive flanges away from said second core. set forth in claim 2 wherein: 

1. Adjustable actuating level current sensing relay comprising: a housing; switch means carried by said housing; Drive means mounted in said housing for actuating said switch means and operative in response to a predetermined voltage to complete a circuit through said switch means; sensing transformer means mounted in said housing and including first and second coil means, said second coil means being connected with said drive means, said transformer means further including first and second spaced apart core means electrically coupled with said first and second coil means and adjustment means coupling said first and second coil means together for adjusting the space therebetween; sensing means connected with said first coil means for sensing the current level in an electrical element whereby said sensing means may be connected with said element, said switch connected with an electrical operator which is to be operated when the current sensed by said sensing means reaches a predetermined level, said adjustment means adjusted to set said first and second core means at a spacing which will provide sufficient electromagnetic coupling therebetween when the current in said current sensing means reaches said predetermined level to produce said predetermined voltage and complete said circuit through said switch means.
 2. Adjustable actuating level current sensing relay as set forth in claim 1 wherein: said second core means includes an axial ferromagnetic core projecting through said first coil means and said second coil means includes a pair of spaced apart ferromagnetic support flanges projecting on opposite ends of said core and wherein said coupling means includes non-ferromagnetic screw means connecting said first and second core means together.
 3. Adjustable actuatiing level current sensing relay as set forth in claim 1 wherein: said adjustment means includes resilient electrically insulative biasing means interposed between said first and second core means and biasing said first and second core means apart.
 4. Adjustable actuating level current sensing relay as set forth in claim 1 wherein: said first core means includes an axial core and said first coil means includes a bobbin removably received on said axial core and including a selected number of electrical coil turns thereon whereby said bobbin may be selectively changed.
 5. Adjustable actuating level current sensing relay as set forth in claim 1 wherein: said first core means includes an axial core and said second core means includes a pair of ferromagnetic flanges projecting transversely therefrom and formed in their extremities with respective first and second bores, said second bore being threaded and wherein, further, said first core means includes an axial ferromagnetic rod and said adjustment means includes nonferromagnetic screw means projecting through said first bore and through said rod, threaded on one extremity, and screwed into said second bore whereby the spacing between said first and second core means may be adjusted by turning said screw means.
 6. Adjustable actuating level current sensing relay as set forth in claim 2 wherein: said adjustment means includes resilient nonferromagnetic biasing means interposed between one end of said axial core and the adjacent flange to maintain said adjacent flange and axial core biased apart.
 7. Adjustable actuating level current sensing relay as set forth in claim 2 wherein: said adjustment means includes first and second resilient non-ferromagnetic biasing means interposed between the opposite ends of said axial core and said respective flanges.
 8. Adjustable actuating level current sensing relay as set forth in claim 3 wherein: at least one of said core means includes a cut back notch for receipt of said biasing means and a projecting contact tab for contacting the other of said core means when said adjustment means is adjusted to draw said first and second core means fully together.
 9. Adjustable actuating level current sensing relay as set forth in claim 5 wherein: said adjustment means includes first and secOnd non-ferromagnetic biasing means interposed between the opposite ends of said first core means and said respective flanges for biasing said respective flanges away from said second core. 